ALOHA	Algorithm that allows multiple terminals to share the same communication channel. Newly arriving packets are transmitted immediately. Packets are retransmitted if no acknowledgement is received. First used in Hawaii.
American Mobile Phone System	AMPS. U.S. Analog cellular phone system.
analog modulation	(traditional) method of transmitting voice signals where the radio carrier wave is directly based on electrical voltages or currents caused by a user speaking into the microphone, or similar transmission of a signal which takes values from a continuous range of values as opposed to from a finite alphabet of values
base station	a land station at a fixed location supporting radio access by mobile users to a fixed communication infrastructure.
Bit Error Rate	BER.
burst	the physical (electric or electromagnetic) contents of a time slot
capture	successful transmission of a data packet despite interference from other terminals transmitting a conflicting signal. Occurs due to differences in received signal power, or signal separation properties of the receiver or the modulation method.
Code Division Multiple Access	CDMA. Multiple access method based on spread spectrum in which different users transmit on (approximately) the same carrier frequency, but use different spreading codes.
cell	the area covered by radio signals from a base station, and in which a mobile station can successfully transmit to a base station
cellular network	Network in which frequencies are reused in a regular pattern, usually with basic area elements of hexagonal shape
cell sectorization	Splitting (theorectically hexagonal) cells into multiple independent sectors (typically 3) that each have their own transmit and receive facilities.
cell splitting	A method of increasing capacity by reducing the size of the cell.
circuit-switching	the allocation of network resources (link capacity, switches) for the entire duration of a communication session.
cluster size	number of different channels needed in a particular frequency reuse plan. Related to reuse distance.
coding	intentional replacement of a set of symbols by another set of symbols. Applications are detection or correction of errors, spectral shaping of the transmit signal, or confidentiality.
collision	conflicting simultaneous transmission by multiple terminals in a random access network.
coverage area	part of the area to which a transmitter gives satisfactory service
Carrier Sense Multiple Access	CSMA. listen before talk
Cordless Telephone ..	CT-0, CT-1, CT-2. various generations of a cordless phone standard.
Digital Audio Broadcasting	DAB.
Dynamic Channel Assignment	DCA.
Digital Communication System	DCS. 1800 MHz version of GSM
decibel	a ratio, expressed as ten times the base-10 logarithm of the ratio of two power levels. This is equivalent to 20 times the base-10 logarithm of the ratio of two voltage, field or current levels.
Digital Enhanced Cordless Telephone	DECT. previously: Digital European Cordless Telephone. Operates in 1800 MHz band.
delay spread	parameter describing the frequency dispersion of a multipath channel. 1) total delay spread: time interval during which delayed reflected waves arrive. 2) rms delay spread: weighted value of interarrival times of reflected waves
digital modulation	A method of transmitting a signal over a radio carrier using symbols of an alphabet of finite size, such as the computer's binary 0s and 1s.
dispersion	variations in the channel transfer amplitude. Frequency dispersion: differences in channels response at different frequencies. Time dispersion: time variations of the channel response
diversity	technique of receiving a radio signal through multiple channels, to improve reliability
doppler spread	(one half times the) width of the spectrum of a received signal when a sinusoidal wave is transmitted over a time dispersive channel
downlink	Originally: A radio link from a satellite to a receiving site on earth or in an aircraft. Now also used for the (forward) link from base station to portable terminal.
Direct Sequence	DS. form of spread-spectrum in which the user signal is multiplied by a fast (spectrally broad) code sequence to increase the transmission bandwidth.
Digital Short Range Radio	DSRR. system for short range communication. For in stance between a car and a roadside base station or gantry.
duplex	Method of operating a network in which transmission is possible simultaneously in both directions of a telecommunications channel.
ERMES	Paging system, originally developed in Europe
equalization	signal processing (filtering) intended to undue channel dispersion. Mostly a compromise is made between combating channel dispersion and avoiding undesirable noise enhancements
erlang	unit of telephone traffic intensity.
European Telecommunications Standards Institute	ETSI. European organization responsible for establishing common industry-wide telecommunication standards.
fading	Time variations of the signal strength received over a radio link. Fading occurs when the several reflected waves (destructively or constructively) interfere with each other.
Federal Communications Commission	FCC. U.S.
Frequency Division Multiple Access	FDMA. Multiple access method in which different users transmit at different carrier frequencies.
flat fading	frequency-nonselective fading. Form of fading that does not cause intersymbol interference.
frequency modulation	FM. analog modulation method, exploiting variations in the instantaneuos carrier frequency
Frequency Shift Keying	FSK. digital frequency modulation method
free space loss	FSL. power loss due to the spreading of energy over the surface of a sphere as the signal travels away from the transmit source.
Geosynchronous Earth Orbit	GEO. satellite communication system.
GMSK	Digital phase (or frequency) modulation method, for instance used in GSM
GSM	previously Groupe de travail Speciale pour les services Mobiles. Widely used digital cellular phone standard, initiated in Europe.
handover	action of changing the handling the operation and control of a radio link from one base station to another as the user moves from one cell to another.
half duplex	communications system that supports conversation in two directions but not simultaneously by sharing a communication path between the two directions
Hertz	unit of measuring the frequency of a signal.
hidden terminal	terminal in a CSMA network actively transmitting data, but which is not noticed by another terminal with data ready for transmission.
Intelligent Network	IN. A secondary network used to create and deliver advanced services to subscribers to public telephone networks (fixed or mobile)
in-phase component	component of a signal that has the same phase as a reference sinusoidal signal.
interference	signals from other emitters than from transmitter sending the wanted signal. Interference differs from noise in that interference often contains similar waveforms as the wanted signal
interleaving	intentional resequencing (shuffling) of the bits in a signal according to a predefined method known by both transmitter and receiver, to avoid burst errors.
IS-95	U.S. Cellular CDMA standard.
Industrial, Scientific and Medical	ISM. bands of the radio spectrum.
Inhibit Sense Multiple Access	ISMA. random access scheme in which the central node broadcasts a busy signal to avoid that terminals start a conflicting transmission when it is receiving data
International Telecommunication Union	ITU.
jamming	Deliberate radiation of electromagnetic energy with the intent to impair the use of electronic systems by the opponent or enemy. Jamming signals can be sinusoidal (CW), noise-like or broadband transmitters, specific deceptive signals that imitate messages.
Japanese Digital Cellular	JDC. now renamed PDC. Operates in the 900 MHz and 1.5 GHz band.
Low Earth Orbiting	LEO. Satellite communication system
matched filter	filter with impulse response which is the time inverse of the expected received waveform. Optimum form of detection in Linear Time-Invariant Additive White Gaussian Noise channel. Can also be implemented as a correlator.
maximum ratio combining	method of prefiltering and adding signals arriving through different branches of a diversity receiver. Follows the principle of the matched filter by weighing a signal proportionally to its amplitude.
microcell	cell with relatively small radius, typically a few hundreds of meters, typically used in a dense cellular network with many subscribers.
mobile station	a user terminal in a radio network intended to be used while in motion or during halts at unspecified points
Mobile Switching Center	MSC. Telecommunications node connecting and controlling several cellular base stations.
multiple access	method that allows multiple spatially separated users to share the same communication channel to a common receiver.
multiplexing	method of combining multiple user signals in a telecommunications switch or base station
noise	random variations in output signal, due to natural of man-induced mechanisms.
noise temperature	ratio of the thermal noise power present in a system over the noise power that would be present a perfect system with only thermal noise, operating at 1 degree Kelvin.
narrowband	1. A radio signal whose bandwidth is smaller than the coherence bandwidth of the dispersive channel, or 2 . A radio signal whose bandwidth is on the order of its information bandwidth, as opposed to spread spectrum.
Nordic Mobile Telephone	NMT. Scandinavian analog cellular telephone system, at 450 or 900 MHz.
Orthogonal Frequency Division Multiplex	OFDM. Multi-carrier modulation method with partially overlapping but nonetheless orthogonal subcarriers.
outage	event during which the signal-to-noise or signal-to-interference ratio is insufficient to allow acceptable performance of the receiver
path loss	(average) propagation attenuation between transmitter and receiver. Depends on distance, antenna heights and atmospheric and terrain properties.
packet	message or a piece of a message, treated as an independent segment of data by the network.
packet switching	the assignment of network resources by splitting the information flow into packets. These are sent from node to node in the network without prior reservations
paging	Communication service that offers one-way transmission of short messages. Typically a paging device (pager) produces an audible 'bleep' when a message arrives.
Personal Communications Network	PCN. usually for short range radio communication but nonetheless with a cellular reuse lay-out. Acronym now often used for DCS 1800.
Personal Communications Service	PCS. In the U.S., a band of a width of 120 MHz has been allocated in the near 1.9 GHz
Personal Communications Service	PCS-1900. U.S. version of GSM, operating in the 1.9 GHz band.
Personal Digital Cellular	PDC. Japanese cellular system.
Phase modulation	PM. Method of modulating a base signal to create an RF signal by varying the phase on a (sinusoidal) carrier wave.
propagation	natural mechanism of dissemination of radio energy
Phase Shift Keying	PSK. digital phase modulation.
quadrature component	component of a signal that is orthogonal to (90 degrees out of phase with) a reference sinusoidal signal.
random access	method or algorithm that allows multiple terminals to share the same communication channel.
rake receiver	special form of a matched filter to detect direct-sequence spread-spectrum signals over a dispersive (multipath) channel. Optimally collects energy received over variously delay propagation paths.
rayleigh fading	fading characterized by a rayleigh probability density of the amplitude, thus an exponentially distributed power. Rayleigh fading typically occurs when an infinitely large number reflected waves with i.i.d. amplitude and amplitude cumulate
Radio Data (Broadcast) System	RDS, RDBS. method to add a data signal to an FM broadcast signal by subcarrier modulation (57 kHz).
reuse	assignment of the same frequency channel in multiple areas, and simultaneous use of these channels allowed by propagation losses between spatially separated areas
reuse distance	distance between the centers of two cells using same frequency channel.
rician fading	fading characterized by a rician probability density of the amplitude. Rician fading typically occurs when a dominant component (say a line-of-sight) plus an infinitely large number reflected waves with i.i.d. amplitude and amplitude cumulate
Radio Frequency	RF. In radio communication baseband signals (voice or data) are modulated onto a carrier and before transmission. Hence, the signal spectrum is shifted to a band where propagation and interference conditions are appropriate.
scattering	dispersion of radio energy caused by reflections
service area	area in which a mobile station can be reached or from where a mobile station can initiate a communication session. Typically includes the coverage areas of multiple cells
simplex	method of operating a network in which transmission is possible only in one direction. No return channel available.
smart antenna	array of antenna elements and associated signal processing, used to improve the performance and to minimize the effect of interference.
spread spectrum	transmission and modulation method that intentionally spreads a signal bandwidth over a wide bandwidth
Total Access Communication System	TACS. analog cellular telephone system in the United Kingdom and Japan, using 25 kHz NBFM channels
Time Division Multiple Access	TDMA. Multiple access method in which different users transmit in different time intervals.
Trans European Trunked Radio Access	TETRA. European digital cellular landmobile radio system for closed user groups
Telecommunications Industry Association	TIA.
thermal noise	random variations in output signal, due to the natural mechanism of motion of electrons.
trunk	in a telephone network, the connection between the switches carrying multiple voice circuits
trunking	use of the radio spectrum in which multiple user groups share the same channels using an automatic multiple access mechanism, thus gaining efficiency
uplink	Originally: A radio link from a site on the earth or from an aircraft to a satellite. Now also used for the (reverse) link from mobile user terminal to base station.
vocoder	Voice coder in which speech is heavily compressed to reduce the channel bit rate required to transmit speech typically to a few hundreds of bits per second
Very Small Aperture Terminal	VSAT. a small mobile or portable satellite communication terminal using small diameter dish antenna.
Vector Sum Excited Linear Predictive	VSELP. Commonly used method for speech coding
Wireless Local Area Network	WLAN. Typically using spread-spectrum transmission in the 2.4 GHz or 5.8 GHz ISM band.
Wireless Local Loop	WLL. The application of radio communication instead of copper wire provide the standard public telephone service.

Displayed: 114 entries in this glossary.